<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<style>
.outer {
  writing-mode:vertical-rl;
  -webkit-writing-mode:vertical-rl;
  width:600px;
  height:200px;
  border:1px solid gray;
  background:#eee;
}
.test1 {
  border:10px solid green;
  margin-top:50%; /* should be 50% of 200px, i.e. 100px */
  width:80px;
  height:30px;
}
.test2 {
  border:10px solid blue;
  margin-right:25%; /* should be 25% of 200px, i.e. 50px */
  margin-left:10%; /* should be 10% of 200px, i.e. 20px */
  width:80px;
  height:30px;
}
.test3 {
  border:10px solid yellow;
  margin-top:10%; /* should be 10% of 200px, i.e. 20px */
  width:80px;
  height:30px;
}
</style>
</head>

<body>

<div class="outer">

<div class="test1">
</div>

<div class="test2">
</div>

<div class="test3">
</div>

</div>

</body>
</html>
